I'm not really sure why this is necessary either, though I'm sure the park has a reason, and probably data to back it up. If they had signage up to remind passholders, it might speed things up by not having people digging around for their IDs. I just give them my pass and ID at the same time and it doesn't take any longer than usual to get me through.
On a side note, on Friday I had the gate attendant question my pass. I have always hated the flimsy plastic passes they issue, so the last time we were in SeaWorld, we opted to pay a couple of bucks for the hard plastic, credit card style passes.
https://seaworldparks.com/en/seaworld-orlando/mako/education-and-conservation/guy-harvey
The gate attendant tried to tell me this wasn't SeaWorld and my pass wasn't valid there XD I assured her it was, and to please try scanning it. She seemed to have no idea SW and BG were related. No big deal, just amusing.